Summary Uncoupling protein 1 (UCP1) mediates non-shivering thermogenesis and, upon cold exposure, is induced in BAT and subcutaneous white adipose tissue (iWAT). Here, by high-throughput screening using the UCP1 promoter, we identify Zfp516 as a novel transcriptional activator of UCP1 as well as PGC1α thereby promoting a BAT program. Zfp516 itself is induced by cold and sympathetic stimulation through the cAMP-CREB/ATF2 pathway. Zfp516 directly binds to the proximal region of the UCP1 promoter, not to the enhancer region where other transcription factors bind, and interacts with PRDM16 to activate the UCP1 promoter. Although ablation of Zfp516 causes embryonic lethality, knockout embryos still show drastically reduced BAT mass. Overexpression of Zfp516 in adipose tissue promotes browning of iWAT even at room temperature, increasing body temperature, energy expenditure, and preventing diet-induced obesity. Zfp516 may represent a future target for obesity therapeutics.

The activation of brown/beige adipose tissue (BAT) metabolism and the induction of uncoupling protein 1 (UCP1) expression are essential for BAT-based strategies to improve metabolic homeostasis. Here, we demonstrate that BAT utilizes actomyosin machinery to generate tensional responses following adrenergic stimulation, similar to muscle tissues. The activation of actomyosin mechanics is critical for the acute induction of oxidative metabolism and uncoupled respiration in UCP1 adipocytes. Moreover, we show that actomyosin-mediated elasticity regulates the thermogenic capacity of adipocytes via the mechanosensitive transcriptional co-activators YAP and TAZ, which are indispensable for normal BAT function. These biomechanical signaling mechanisms may inform future strategies to promote the expansion and activation of brown/beige adipocytes.

SUMMARY Zfp516, a brown fat (BAT) enriched and cold-inducible transcription factor, promotes transcription of UCP1 and other BAT-enriched genes for non-shivering thermogenesis. Here, we identify lysine specific demethylase 1 (LSD1) as a direct binding partner of Zfp516. We show that, through interaction with Zfp516, LSD1 is recruited to UCP1 and other BAT-enriched genes, such as PGC1α, to function as a coactivator by demethylating H3K9. We also show that LSD1 is induced during brown adipogenesis and that LSD1 and its demethylase activity is required for the BAT program. Furthermore, we show that LSD1 ablation in mice using Myf5-Cre alters embryonic BAT development. Moreover, BAT-specific deletion of LSD1 via the use of UCP1-Cre impairs the BAT program and BAT development, making BAT to resemble WAT, thereby reduces thermogenic activity, promoting obesity. Finally, we demonstrate in vivo requirement of Zfp516-LSD1 interaction for LSD1 function in BAT gene activation.

White adipose tissue (WAT) is the primary energy storage organ and its excess contributes to obesity, while brown adipose tissue (BAT) and inducible thermogenic (beige/brite) adipocytes in WAT dissipate energy via Ucp1 to maintain body temperature. BAT and subcutaneous WAT develop perinatally while visceral WAT forms after birth from precursors expressing distinct markers, such as Myf5, Pref-1, Wt1, and Prx1, depending on the anatomical location. In addition to the embryonic adipose precursors, a pool of endothelial cells or mural cells expressing Pparγ, Pdgfrβ, Sma and Zfp423 may become adipocytes during WAT expansion in adults. Several markers, such as Cd29, Cd34, Sca1, Cd24, Pdgfrα and Pref-1 are detected in adult WAT SVF cells that can be differentiated into adipocytes. However, potential heterogeneity and differences in developmental stage of these cells are not clear. Beige cells form in a depot- and condition-specific manner by de novo differentiation of precursors or by transdifferentiation. Thermogenic gene activation in brown and beige adipocytes relies on common transcriptional machinery that includes Prdm16, Zfp516, Pgc1α and Ebf2. Moreover, through changing the chromatin landscape, histone methyltransferases, such as Mll3/4 and Ehmt1, as well as demethylases, such as Lsd1, play an important role in regulating the thermogenic gene program. With the presence of BAT and beige/brite cells in human adults, increasing thermogenic activity of BAT and BAT-like tissues may help promote energy expenditure to combat obesity.

SUMMARY Brown adipose tissue harbors UCP1 to dissipate chemical energy as heat. However, the transcriptional network that governs the thermogenic gene program is incompletely understood. Zc3h10, a CCCH-type zinc finger protein, has recently been reported to bind RNA. However, we report here that Zc3h10 functions as a transcription factor to activate UCP1 not through the enhancer region, but by binding to a far upstream region of the UCP1 promoter. Upon sympathetic stimulation, Zc3h10 is phosphorylated at S126 by p38 mitogen-activated protein kinase (MAPK) to increase binding to the distal region of the UCP1 promoter. Zc3h10, as well as mutant Zc3h10, which cannot bind RNA, enhances thermogenic capacity and energy expenditure, protecting mice from diet-induced obesity. Conversely, Zc3h10 ablation in UCP1+ cells in mice impairs thermogenic capacity and lowers oxygen consumption, leading to weight gain. Hence, Zc3h10 plays a critical role in the thermogenic gene program and may present future targets for obesity therapeutics.

In contrast to white adipose tissue (WAT) that stores energy in the form of triglycerides, brown adipose tissue (BAT) dissipates energy by producing heat to maintain body temperature by burning glucose and fatty acids in a process called adaptive thermogenesis. The presence of an inducible thermogenic adipose tissue, and its beneficial effects for maintaining body weight and glucose and lipid homeostasis, have raised intense interest in understanding the regulation of thermogenesis. Elucidating the regulatory mechanisms underlying the thermogenic adipose program may provide excellent targets for therapeutics against obesity and diabetes. Here, we review recent research on the role of epigenetics in the thermogenic gene program, focusing on DNA methylation and histone modifications.

Brown adipose tissue (BAT) is specialized to burn fuels to perform thermogenesis in defense of body temperature against cold. Recent discovery of metabolically active and relevant amounts of BAT in adult humans have made it a potentially attractive target for development of anti-obesity therapeutics. There are two types of brown adipocytes: classical brown adipocytes and brown adipocyte-like cells, so-called beige/brite cells, which arise in white adipose tissue in response to cold and hormonal stimuli. These cells may derive from distinct origins, and while functionally similar, have different gene signatures. Here, we highlight recent advances in the understanding of brown and beige/brite adipocytes as well as transcriptional regulation for development and function of murine brown and beige/brite adipocytes focusing on EBF2, IRF4, and ZFP516, in addition to PRDM16 as a coregulator. We also discuss hormonal regulation of brown and beige/brite adipocytes including several factors secreted from various tissues, including BMP7, FGF21, and irisin, as well as those from BAT itself, such as Nrg4 and adenosine.

No abstract